SCL-SYD non stop on QF. J seats will be flat or sloping (depends on the retrofit of the 744 equipment.
SCL-AKL-SYD one stop on LA. J seats are flat. The stop may be a grind if you manage to sleep. If LA is really late leaving SCL, it will stop in AKL and you'll be put on a QF, NZ or EK flight to get you over to SYD. This allows that LA aircraft to regain its schedule for the return AKL-SCL sector.
The QF flight may fly further south than LA and you might have a chance of seeing Antarctica (but YMMV).
Although I prefer the LA service and quietness of their 343 aircraft, you might be better off on QF. But QF don't serve pisco sours.